Trauma or irritation can certainly cause normal moles to bleed. We see this all the time. However, bleeding should always raise some concern and prompt further investigation. As skin cancers grow, they are often more fragile than normal skin. These skin cancers may bleed spontaneously (without a reason) or bleed more easily from relatively light trauma. For example, some patients notice a skin cancer on their face because it always seems to bleed when they dry off with a towel after taking a shower, or easily bleeds when shaving their face. Of course, you can also cut a normal mole while shaving!
